1. Field of the Invention:
The present invention relates to a control apparatus, a control method, and an engine control unit for a variable cylinder internal combustion engine which can be operated either in a full cylinder operation mode for operating all of a plurality of cylinders or in a partial cylinder operation mode for pausing some of the plurality of cylinders using a cylinder pausing mechanism, and more particularly, to such a control apparatus, a control method, and an engine control unit for controlling an idling rotational speed, deceleration fail cut, and driving of an auxiliary engine.
2. Description of the Prior Art:
Conventionally, Laid-open Japanese Patent Application No. 2002-221055, for example, describes a controller for a variable cylinder internal combustion engine. The variable cylinder internal combustion engine described therein is a V-type six-cylinder one which comprises a cylinder pausing mechanism for switching one half of the cylinders, i.e., three variable cylinders between an operation mode and a pause mode. In the variable cylinder internal combustion engine, the controller controls the cylinder pausing mechanism and injectors to switch valve actuating mechanisms associated with the three variable cylinders from the operation mode to the pause mode, thereby switching the three variable cylinders from the operation mode to the pause mode. Simultaneously, a fuel injected into the three variable cylinders is stopped, thereby switching the three variable cylinders from the operation mode to the pause mode. On the other hand, an operation reverse to the foregoing results in the three variable cylinders being switched from the pause mode to the operation mode. Stated another way, the variable cylinder internal combustion engine is operated either in a full cylinder operation mode in which all of the six cylinders are driven, or in a partial cylinder operation mode in which the three variable cylinders are made inoperative.
The controller conducts the switching control for switching the engine from the partial cylinder operation mode to the full cylinder operation mode by operating the valve actuating mechanisms for the three variable cylinders, while suspending the injection of the fuel to the three variable cylinders, determining whether or not a valve actuating system including the valve actuating mechanisms are normally operating in accordance with a subsequent detection signal from a LAF sensor, and stopping the subsequent injection of the fuel to the three variable cylinders upon determination of a fault in the valve actuating system for the three variable cylinders. In other words, the operation of the three variable cylinders is stopped.
The conventional controller described above has the disadvantage of low controllability and inability to appropriately control the variable cylinder internal combustion engine under a variety of operating conditions because the controller does not perform particular control operations other than that for stopping the injection of the fuel into the three variable cylinders, i.e., for stopping the operation of the three variable cylinders when the controller determines a fault in the valve actuating system for the three variable cylinders. For example, assume that the controller is designed to conduct a rotational speed control during an idling operation (hereinafter called the “idling rotational speed control”) If a fault in the valve actuating system results in the number of operable cylinders reduced to three, resulting lower combustion energy of the internal combustion engine as a whole makes it difficult to continue the idling operation while overcoming a load such as friction of the variable cylinder internal combustion engine, possibly causing in the variable cylinder internal combustion engine to stop. Likewise, during the deceleration fuel cut operation for stopping the supply of a fuel to cylinders for decelerating the vehicle, or in an auxiliary machinery control for an air conditioner and the like, a fault as mentioned above would prevent the variable cylinder internal combustion engine from continuing the operation, while overcoming the load, for the same reason, possibly causing the variable cylinder internal combustion engine to stop.